The present invention relates to high-volume reproduction systems and methods and more particularly to duplicator systems and methods structured for efficient high-volume reproduction in the collated duplex mode.
There are a variety of commercial applications of reproduction technology where a need exists to reproduce manuals or books, or sets thereof, containing up to thousands of pages that are suitably assembled such as in three-ring binders or in bound units. A large number of book copies may be required for distribution to users or customers. Applications like these are called high-volume applications.
In particular high-volume applications, the books may have to be revised or updated periodically, such as every three or six months. In the revision process, some but normally not all pages will be modified and some pages may be deleted or added. In many cases, trade practices or regulatory requirements may make it necessary to reproduce the entire revised book or set of books as opposed to reproducing insert pages for appropriate placement in the original book copies. In any case, the page insert approach is typically undesirable because it is labor intensive and because of the likelihood of assembly errors.
The original text, graphics, and photographs, that constitute the book content, may reside in multiple sources. For example, an original may reside on microfilm, in electronic storage, on standard 81/2".times.11" paper, or on "paste-ups". Originals from which reproductions are to be made are derived from the multiple storage sources and placed on one or more selected media.
A typical commercial application in which high-volume reproduction technology is needed is that in which a manufacturer makes and sells relatively complex products for which maintenance books must be issued and revised from time to time. The production of maintenance books for a product which may be supplied in a variety of forms or models typically is relatively complex because of book differences that are required for different models and/or customers.
Offset lithography is one process that has often been used for high-volume reproduction, but it is typically relatively expensive. In this process, extensive setup time is required for building each master original or revised original. Relatively high pressman labor operating costs are incurred, and up to 10% of the total copy output constitutes waste copies caused by process adjustment during job startup and shutdown. It is noteworthy, however, that offset lithography does in general provide high resolution production of photographic originals.
Large output sorters, having multiple towers containing up to 600 or more bins, have been employed in offset lithography to support post-collation book production for high-volume jobs. However, the operation of such sorters and the lithography production process as a whole has been relatively inflexible especially in terms of accommodating more complex jobs that involve varying production requirements within a particular job or from job to job. Such inflexibility stems from the very nature of the whole lithographic reproduction and sorting process along with an absence of process controls that, if implementable at all, could otherwise facilitate the creation of added process flexibility.
In high-volume jobs that require "limitless" sorting, that is, a number of copies greater than the machine reproduction capacity, typically the operator of the lithography process must determine the job breakup and run the job parts accordingly. Another example of relative inflexibility in the offset lithography process is that in which some book copies may require certain pages to be different from corresponding pages in other book copies. While the lithography process may be operated to permit collation of the proper page copies in the various book copies, such process operation is highly inefficient, costly and inconvenient.
An additional example of flexibility limits in the offset lithography process is that in which a capability is needed for job parking at the end of work shifts. A job is parked when work is left in sorter bins at the end of a shift and the job is picked up again on the next shift, often the next day. The lithography pressman has limited system hardware support in resuming the parked job and completing it.
Pre-collation copying with use of a duplicator is another process that has been used for reproducing multiple copies of original manuals or books. However, the machine capacity limits successive segment sizes which therefore must be "hand-married" or manually collated after production. Copy integrity is also a problem in the pre-collation reproduction process. Thus, an occasional skewing of an original document on the platen glass requires inspection of all output copies to uncover any skewed ones and thereby assure copy product quality. Such inspection is impractical for high-volume jobs.
Another process that lends itself to high-volume reproduction is a process in which post-collation copying is performed with use of a duplicator and a high capacity sorter. Generally, the availability of electronic control with a duplicator provides a basic capability for creating process flexibility in high-volume reproduction jobs.
As compared to a pre-collation duplicator process, a post-collation duplicator process facilitates the performance of highly complex jobs because the layout of collation bins allows for the tailoring of some book copies to meet the requirements of particular customers or particular product models. Moreover, possible future commercial use of a common electronic format for source originals could be efficiently implemented in high-volume reproduction jobs with the use of electronically controlled duplicators.
High-volume, post-collation duplicators have been generally unavailable commercially because of a lack of required technology development.
More specifically, in a high-volume reproduction system, the sorter is structured with a plurality of multiple-bin towers thereby providing a high volume of bins for sorting. For example, the sorter may contain up to 600 or more bins with each bin having a maximum capacity of 100 sheets.
In the collated duplex mode, a large job has to be broken into job segments which are sized as a function of the duplex tray capacity, the requested copy quantity, the number of bins available and the number of bins allocated per output set. Multiple bins are required for an output set if the size of the set exceeds the sheet capacity of a single bin.
The duplex tray in a duplicator temporarily holds copy sheets during the duplex copying process and normally has a limited capacity, such as 100 sheets. Thus, the copy sheet capacity of the high-volume sorter bin is much greater than the number of copies that the duplex tray can deliver in a single pass. The manner in which copies are delivered to form collated sets in the sorter towers affects copy reliability and system and operator efficiency.
Copy reliability tends to increase as the number of copies made per placement of an original document increases, principally because the probability of a skewed placement of an original increases with increasing placements of originals. Further, sorting efficiency is enhanced through facilitated operator unloading if the sorter is loaded one tower at a time, since the operator unload process then progresses in a logical sequence especially when the system is executing the entry job in the limitless mode. In limitless operation, the operator unloads one job segment as another job segment is being delivered to the sorter, and this load-unload process continues until the job is completed.
In the illustrative case of a tower having 60 bins, a reasonable balance exists among copy reliability, system efficiency and operator unloading facility when copy distribution is scheduled as tower-by-tower loading with an allocation of a single bin for each set. In that case, the job segment size is 60 copies which provides a reasonable utilization of the duplex tray as well as the original document handler and opera unloading is facilitated since unloading of a job segment is simply achieved by unloading the single tower.
However, if more than one bin is used per set because of set size, duplex tray and automatic document handler utilization is reduced in a tower-by-tower load process. In the illustrative example of 60-bin towers, the number of bins per set may, for example, be 1, 2, 3, 4, 5, or 6. With copy distribution scheduled as tower-by-tower loading, duplex tray and automatic document handler utilization would be 60, 30, 20, 15, 12, and 10 copies, respectively. Thus, with the tower-by-tower scheduling, system efficiency, i.e. duplex tray and document handler utilization, decreases significantly with increasing set sizes that require increasing numbers of bins per set.